1. Field of the Invention
The present invention relates to an image recording apparatus suitably used for a copying or facsimile machine for recording image information on a recording medium.
2. Related Background Art
A typical example of an apparatus of this type is a so-called dual mode copying machine in which information such as a date, and characters input from a host computer or the like are recorded by a sub-record optical system while an original is copied by a main record optical system. The sub-record optical system may comprise a laser having a larger light output than that of an LED (Light-Emitting Diode), which is used to erase an unnecessary portion of an image, in addition to image recording.
When a laser is used as a sub-record optical system, generally, the value of a current supplied to the laser is adjusted by properly controlling the time interval of the losing because the optical output (light quantity) is changed as a function of temperature. A typical conventional adjustment method is performed as follows. A sensor is arranged to monitor the optical output from the laser, and the laser is then deenergized. Thereafter, a current is gradually increased, and the current increase is stopped when the sensor output reaches a predetermined value.
When such conventional control method is employed, the optical output is temporarily stopped (OFF), an unintended and undesired black image is formed in background scanning, that is, in the case that a portion irradiated with a laser beam is recorded in white, for example.
When a laser is used in a sub-record optical system to erase an unnecessary image portion at the start of recording, copying cannot be started until a rotatable polygonal mirror for laser scanning is brought to a steady rotational speed. In addition, the ON time of the laser is prolonged to shorten the mechanical service time of the apparatus, thus degrading reliability of the apparatus.
In multifunction of an image recording apparatus, such as copying machines, in recent years, functions such as a variable magnification function, an automatic density adjustment function, an automatic paper size selection function, an automatic magnification selection function, a multicolor copying function, an automatic both sides recording function, an image editing function, a two-color development function with one-button operation, a page consecutive copying function, and a binding margin adjustment function have been available. At present, combinations of these functions are also required.
In such a conventional apparatus a described above, it is expected to easily emphasize image information.
Examples of apparatus for recording an image on a common recording medium by using a plurality of light sources are described in U.S. Pat. Nos. 4,552,449, 4,346,982, 4,378,156 and 4,517,579, and U.S. Ser. No. 893,358 (filed Aug. 5, 1986). There is much room left for further improvements.